Exam 2 (Ch. 4,5,6) Notes A&P.docx

### **Ch. 4: Genes & Cellular Function** **4.1- DNA & RNA, the Nucleic Acids** A. DNA Structure & Function \- DNA & Nucleic acids are polymers of nucleotides -Consist of a sugar, phosphate group & single or double ringed nitrogenous base →Cytosine (C) & Thymine (T) = single NR (pyrimidines) →A...

### **Ch. 4: Genes & Cellular Function** **4.1- DNA & RNA, the Nucleic Acids** A. DNA Structure & Function \- DNA & Nucleic acids are polymers of nucleotides -Consist of a sugar, phosphate group & single or double ringed nitrogenous base →Cytosine (C) & Thymine (T) = single NR (pyrimidines) →Adenine (A) & Guanine (G) = double NR (purines) \- Double Helix: each side piece is a phosphate group alternating w/ deoxyribose, \"steps\" are nitrogenous bases -Law of Complementary Pairs: A-T + G-C →a purine ALWAYS pairs with a pyrimidine; gives structure its 2nm width -Watson & Crick - determined DNA structure, stole data from Rosalind Franklin (who discovered double helix)g -Humans have est. 22,300 genes (2% of DNA) other 98% don\'t code for proteins but play a role in gene activity B. Chromatin & Chromosomes **-** DNA in the nucleus is *Chromosomes* (DNA + Proteins forming chromatin) in the nucleus: DNA winds around histones (protein spools), forming core particles 1. 2. -DNA is damaged 10-100,000x daily & is maintained by repair enzymes that undo damage -Chromosomes are located in territories (w/ channels for regulatory chem. access) & can migrate as cells develop When preparing to divide (visible w light microscope): 1. 2. -Centromere: where sister chromatids are pinched together, has a Kinetochore (protein that allows spindle fiber attachment) on each side C. RNA vs. DNA +-----------------------+-----------------------+-----------------------+ | Feature | Deoxyribonucleic Acid | Ribonucleic Acid | +=======================+=======================+=======================+ | Sugar | Deoxyribose | Ribose | +-----------------------+-----------------------+-----------------------+ | Types of Nucleotide | Adenine (A) , Thymine | Adenine (A) , Uracil | | Bases | (T), | (U), | | | | | | | Cytosine (C), Guanine | Cytosine (C), Guanine | | | (G) | (G) | +-----------------------+-----------------------+-----------------------+ | \# of Nucleotide | Averages 10\^8 base | Averages 70-10,000 | | Bases | pairs | bases (mostly | | | | unpaired) | +-----------------------+-----------------------+-----------------------+ | \# of Nucleotide | Two (double helix) | One | | Chains | | | +-----------------------+-----------------------+-----------------------+ | Site of Action | In nucleus | In cytoplasm | +-----------------------+-----------------------+-----------------------+ | Function | Codes for RNA/protein | Carries out DNA | | | synthesis | instructions; protein | | | | synth. | +-----------------------+-----------------------+-----------------------+ #### **4.2- Genes & Their Actions** A. What is a Gene? -A gene is an info containing segment of DNA that codes for RNA -Amino Acid sequence is determined by nucleotide sequence \- Single Nucleotide Polymorphism accounts for genetic variation in humans -Humans have 46 chromosomes, 1 (23 chromosomes) genome from each parent →99.9% genetically identical, still 3 mil. differing base pairs → Gene Rich: 17,19,22 & Gene Poor: Y, 4, 8, 13, 18, 21 -Total genome is made up of 3.1 billion nucleotide pairs, 3,000-2.4 million long B. The Genetic Code -A base triplet is made of 3 nucleotides -Codon: mRNA/DNA sequence, based on base triplets (trinucleotide) -64 possible codons represent amino acids → 3/64 are STOP codons, AUG is methionine & a START codon C. Protein Synthesis (Transcription & Translation) [Transcription:] RNA polymerase "unzips" DNA double helix 17 base pairs at a time, adding complementary NBs & rewinding → can be transcribed by multiple RNA polymerase at a time -transcription makes a "first draft" pre-mRNA, made of exons (translate protein) & introns (removed before translation) → enzymes splice exons (EXIT) together & cut out introns (stay IN) to make functional mRNA → intron codes for regulatory non-coding RNAS (ncRNAS) that stay IN the nucleus [Translation:] RNA→Protein 1. 2. a. b. c. 3. -average proteins are 400 amino acids long, having a minimum of 1,203 nucleotides D. Protein Processing & Secretion -New proteins often have older chaperone proteins accompanying them -Free Ribosomes make enzymes/proteins used in cytosol -ER makes packaged/secreted enzymes E. Gene Regulation -Genes are turned on/off as needed, many are permanently off -controlled by regulatory proteins F. Synthesizing other Substances -enzymatic reactions produce glycogen, fat, steroids, phospholipids, pigments, & more -can convert substances to other things -RNA/DNA only code for protein but control other things indirectly #### **4.3- DNA Replication and the Cell Cycle** A. DNA Replication 1. 2. a. 3. b. 4.  B. Mistakes & Mutations -DNA Damage Response (DDR): DNA polymerase checks itself & corrects mistakes with high accuracy → mistakes are 1 in 1 million -mutations come from radiation, chemicals, & viruses E. Regulation checkpoints G1: determines if cell is ready to divide, G2: assesses DNA replication, M: allows cell to finish mitosis/cytokinesis C. The Cell Cycle -G1: first gap phase, cell synths. new proteins, grows, & accumulates DNA replication materials -S: synthesis, cell duplicates centrioles & nuclear DNA, S-C replication occurs -G2: second gap, interval between DNA rep. & cell division; synthesizes enzymes, checks DNA, grows D. Mitosis Prophase: chromatin condenses into visible chromosomes Metaphase: chromosomes line up in middle & prep to divide Anaphase: chromosomes separate @ centromere & are are pulled in opposite directions by spindle fibers Telophase: spindle disappears, nuclei form, chromosomes revert to chromatin →cytokinesis: physical division of the cells by myosin & actin, does not always occur (multinuclear cells) #### **4.4- Chromosomes & Heredity** A. The Karyotype -Heredity = transmission of genetic characteristics from parent→offspring -Karyotype: an individual\'s complete set of chromosomes, charted out including traits, size, \#, shape, etc. -Homologous Chromosomes: each set of 23 pairs →1 set from each parent -Sex Chromosomes: determine an individual\'s sex (XX= Female, XY= Male) -Autosomes: all non-sex chromosomes -Diploid: cell w/ 23 chromosome pairs (ie. somatic cells) -Haploid: cell w 23 unpaired chromosomes (ie. germ/sex cells) B. Genes & Alleles -Locus: the position of a gene -Allele: alternative form of a gene, produces a trait, same locus as base gene →dominant or recessive -Homozygous = identical alleles on both chromosomes -Heterozygous = different alleles -Genotype: paired alleles for a given trait -Phenotype: how a gene is expressed physically →expressed alleles show up in phenotype Punnett Square: a diagram showing inheritance patterns of a gene ### **Chapter 5: Tissues** #### **5.1- The Study of Tissues** A.4 **Tissue Classes** -Epithelial, connective, nervous & muscular -tissue: a group of similar cells that arise from the same embryonic region & work together \- the 4 types differ in type/function of cell, matrix characteristics & total space occupied -Matrix: composed of fibrous proteins & a ground substance, tissue fluid, efc, or interstitial fluid -Ground Substances: contain water, gasses, minerals, nutrients wastes, hormones & other chemicals →where cells obtain/release substances C.**Histology** -Histological sections: thin slices of tissue mounted on slides -Histological stains: performed to enhance detail, different stains for different structures -Longitudinal (long ways), oblique (slanted), & cross (horizontal) sections #### **5.2- Epithelial Tissue** A. Overview -consists of sheets of closely adhering cells, 1+ thick, upper surface usually exposed to environment/internal surface \- serve as protection, secretion, excretion, absorption, filtration, sensation -Basement Membrane: connective tissue base under epithelium -Basal Surface: surface of epithelial cell; faces basement membrane -Lateral surface: both sides of cell; face adjacent cells -Apical surface: top of cell; faces lumen/body surface B.Simple -consists of one layer of cells →squamous, cuboidal, or columnar -pseudostratified: not all cells reach surface but all touch basement membrane -goblet cells: wine-glass shaped, line mucous membranes (produce mucus) C.Stratified -2-20+ layers →squamous, cuboidal, or columnar -keratinized (st. squamous): packed w/ keratin, retards water loss, resists penetration, layer of dead skin cells #### **5.3- Connective Tissue** A. Overview -most abundant in body, widely distributed, histologically variable →fibrous, adipose, cartilage, bone, blood -binds organs, provides support, physical & immune protection, movement, storage, heat, & transport -\*"rule"= all cells occupy less space than ec matrix, usually do not directly touch. Cells: B. Fibrous Collagenous: collagen based, resist stretching, tough & flexible, tendons/ligaments Reticular: thin collagen fibers w/glycoprotein coat, spongy organs, basement membrane Elastic: thinner, branch & rejoin each other, made of elastin coated w/glycoprotein (fibrillin), coiled structure, able to stretch/recoil Loose: more ground substance than fibers Dense: fibers occupy more space than cells & ground substance, closely packed Areolar tissue: loosely organized fibers, abundant blood vessels, empty space, provides nutrition to cells, mostly collagenous, ready supply of leukocytes, highly variable in appearance Reticular: mesh of reticular fibers & fibroblasts, framework/stroma of lymph nodes, spleen, thymus, bone marrow, space Dense regular: closely packed collagen fibers, little open space, parallel fibers (regular), found in tendons/ligaments, strong, more/mostly fibroblasts Dense irregular: similar to reg. fibers, run in random directions, resist unpredictable stress, protective capsules C. Adipose -Adipocytes: dominant cell type, occur singly/small clusters in areolar Space between is occupied by areolar, reticular & capillaries -White/yellow fat: most abundant adult tissue, insulation, anchors, cushions, contribute to body contours, secretes hormones, regulates metabolism (energy) -Brown fat: heat generating, protection from cold stress & hypothermia, more numerous mitochondria, responds to sympathetic nervous system, stimulates mito. to break down & store lipids, critical to infants D. Cartilage -relatively stiff, flexible, rubbery matrix, provides shape & support -produced by chondroblasts, secrete matrix & surround themselves, form lacunae (cavities) -no blood capillaries, waste/nutrients diffuse thru matrix via solute diffusion, slow metabolism & cell diffusion -matrix is rich in glycosaminoglycans & varies in fiber composition (variously thick fibers) -3 classes: hyaline, elastic, fibrocartilage E. Bone -hard, calcified connective tissue, can refer to entire bone or just osseous tissue →composed of osseous tissue, cartilage, marrow, etc.\ Spongy: fills long bone heads & middle of flat bones\ Compact: dense, no spaces, wild, external surface of bone -most is arranged around central (osteonic) canals, bvs & nerves travel through -Bone matrix is deposited in concentric lamellae (onion-like layers around canal), canal + lamellae = osteon -Lacunae between lamellae occupied by osteocytes (mature) -Channels called canaliculi penetrate each lacuna -\> allow for contact between neighboring osteocytes -Bone is covered by periosteum (tough, fibrous membrane) F. Blood -fluid connective tissue, travels through blood vessels, transports cells & substances -comprised of plasma (gs), erythrocytes (rc), leukocytes (wbc) & platelets -formed elements: plasma & its cellular components -produced by connective tissue of marrow & lymphoid organs -blood doesn\'t exhibit fibers unless it is clotting #### **5.3- Excitable Tissues** A.Nervous specialized for communication via electrical/chemical signals Consists of neurons (nervous cells) & many more neuroglia (glial cells) Neurons: detect stimuli & respond, transmit coded messages to other cells rapidly round/ovoid/stellate body, dendrites & axon/nerve fibers Glial: protect & assist neurons B.Muscle -Excitable, specialized to contract when stimulated & exert force on other tissue, fluids, or organs→responsible for body movement, digestion, breathing, waste elimination, speech & blood circulation -Striation: alternating light and dark bands or discs that cross striated muscles at right angles to their long axes\ Skeletal: long, threadlike muscle fibers, ctrls voluntary movements, striated\ Cardiac: limited to ♥️, cardiomyocytes, striated, much shorter, involuntary & branched/notched @ ends, 1-2 nuclei, have intercalated discs that prevent contractions from separating cells\ Smooth: lacks striation, involuntary, fusiform & relatively short, mostly visceral #### **5.5- Gaps, Glands, & Junctions** A. Junctions Tight junction: completely encircles an epithelial cell near apical surface, joins neighboring cells w/adhesion proteins →Prevents substances to pass between epithelial cells, ensures most nutrients pass through epithelial cells Desmosomes: Patch that holds cells together, can\'t prevent substances from passing →Keeps cells from pulling apart & resists mechanical stress -Gap junctions: formed by connexon, Ions, glucose, amino acids, and other solutes pass between cells -Connexons: Six transmembrane proteins arranged in a ring surrounding a water-filled channel B. Glands -A gland is a cell or organ that secretes substances for use elsewhere in the body →Synthesized by glandular cells or removed from others & modified →Secretion= useful to body, Excretion= waste product -Endocrine glands: release their secretion directly into the blood or lymph (ductless glands), many capillaries -Exocrine glands: release their secretion onto an epithelial surface via a duct →simple= single unbranched duct, compound= branched duct →tubular= duct & secretory portion are one uniform diameter, actinus/alveolus= secretory forms a sac Modes of Secretion: eccrine, apocrine, holocrine\ Eccrine: secrete via exocytosis\ Apocrine: substance coalesces in cytosol & buds from cell surface\ Holocrine: gland cells accumulate products & disintegrate to release it C. Membranes -Cutaneous: the skin; stratified squamous epithelium resting on connective tissue -Mucous: lines passages that open to the external environment, epithelium resting on areolar & smooth muscle -Serous: produce watery fluid; simple squamous epithelium resting on areolar connective tissue #### **5.6- Tissue Growth, Development, Repair, & Degeneration** A. Growth -Tissues grow because their cells increase in \# or size -Hyperplasia: cells multiply in number (childhood & embryonic) -Hypertrophy: enlargement of pre-existing cells -Neoplasia: growth of a tumor, also called a neoplasm B. Tissue Repair -Regeneration: replacement of damaged tissue w same cells, full function restoration -Fibrosis: replacement of damaged area with scar tissue -Remodeling: tissue repair, lasts up to 2 years C. Degeneration & Death -Atrophy: shrinkage in tissue due to loss in cell size or \# (senile or disuse) -Necrosis: pathological tissue death due to trauma, toxins, infection, etc →infarction (sudden, loss of blood supply) or gangrene (infection, obstructed blood supply)